Custom data types #106
Description
I am looking into migrating to sqlpp23. I found one issue.
I am using a lot of strong types. Mapping enum fields in the database to enum fields in C++, strong typed id's, so that mistakes like: tableA_id == tableB_id cannot happen. Well, a small reproducible example says more then words:
#include <sqlpp23/mock_db/mock_db.h> #include <sqlpp23/sqlpp23.h> #include <sqlpp23/tests/core/make_test_connection.h> // Strong type struct TestId { int64_t value{0}; explicit TestId(int64_t v) : value(v) {} TestId() = default; bool operator==(const TestId&) const = default; }; // Table definition struct Test_ { struct Id { SQLPP_CREATE_NAME_TAG_FOR_SQL_AND_CPP(id, id); using data_type = TestId; // <-- strong type as data_type using has_default = std::false_type; }; struct Symbol { SQLPP_CREATE_NAME_TAG_FOR_SQL_AND_CPP(symbol, symbol); using data_type = ::sqlpp::text; using has_default = std::false_type; }; SQLPP_CREATE_NAME_TAG_FOR_SQL_AND_CPP(stock, stock); template<typename T> using _table_columns = sqlpp::table_columns<T, Id, Symbol>; using _required_insert_columns = sqlpp::detail::type_set< sqlpp::column_t<sqlpp::table_t<Test_>, Id>, sqlpp::column_t<sqlpp::table_t<Test_>, Symbol>>; }; using Test = ::sqlpp::table_t<Test_>; // Glue needed for sqlpp template <> struct sqlpp::data_type_of<TestId> { using type = sqlpp::integral; }; template <typename Context> auto to_sql_string(Context& ctx, const TestId& id) { return to_sql_string(ctx, id.value); } template <> struct sqlpp::result_data_type_of<TestId> { using type = TestId; // result row will hold a TestId directly }; // End glue int main() { auto db = sqlpp::mock_db::make_test_connection({}); const Test stock; for (const auto& row : db(select(all_of(stock)).from(stock))) { TestId id = row.id; (void)id; } return 0; }Compiling with: clang++ -std=c++23 -I include -I tests/include test.cpp gave the following output:
In file included from test.cpp:1: In file included from include/sqlpp23/mock_db/mock_db.h:30: In file included from include/sqlpp23/mock_db/database/connection.h:32: include/sqlpp23/core/query/result_row.h:55:12: error: no matching member function for call to 'read_field' 55 | target.read_field(index, _field::operator()()); | ~~~~~~~^~~~~~~~~~ include/sqlpp23/core/query/result_row.h:72:36: note: in instantiation of function template specialization 'sqlpp::detail::result_field<0, sqlpp::field_spec_t<Test_::Id::_sqlpp_name_tag, TestId>>::_read_field<sqlpp::mock_db::text_result_t>' requested here 72 | (result_field<Is, FieldSpecs>::_read_field(target), ...); | ^ include/sqlpp23/core/query/result_row.h:134:12: note: in instantiation of function template specialization 'sqlpp::detail::result_row_impl<std::integer_sequence<unsigned long, 0, 1>, sqlpp::field_spec_t<Test_::Id::_sqlpp_name_tag, TestId>, sqlpp::field_spec_t<Test_::Symbol::_sqlpp_name_tag, sqlpp::text>>::_read_fields<sqlpp::mock_db::text_result_t>' requested here 134 | _impl::_read_fields(target); | ^ include/sqlpp23/core/query/result_row.h:151:9: note: in instantiation of function template specialization 'sqlpp::result_row_t<sqlpp::field_spec_t<Test_::Id::_sqlpp_name_tag, TestId>, sqlpp::field_spec_t<Test_::Symbol::_sqlpp_name_tag, sqlpp::text>>::_read_fields<sqlpp::mock_db::text_result_t>' requested here 151 | row._read_fields(target); | ^ include/sqlpp23/mock_db/text_result.h:92:42: note: in instantiation of function template specialization 'sqlpp::detail::result_row_bridge::read_fields<sqlpp::field_spec_t<Test_::Id::_sqlpp_name_tag, TestId>, sqlpp::field_spec_t<Test_::Symbol::_sqlpp_name_tag, sqlpp::text>, sqlpp::mock_db::text_result_t>' requested here 92 | sqlpp::detail::result_row_bridge{}.read_fields(result_row, *this); | ^ include/sqlpp23/core/result.h:70:13: note: in instantiation of function template specialization 'sqlpp::mock_db::text_result_t::next<sqlpp::result_row_t<sqlpp::field_spec_t<Test_::Id::_sqlpp_name_tag, TestId>, sqlpp::field_spec_t<Test_::Symbol::_sqlpp_name_tag, sqlpp::text>>>' requested here 70 | _result.next(_result_row); | ^ include/sqlpp23/core/clause/select_column_list.h:166:12: note: in instantiation of member function 'sqlpp::result_t<sqlpp::mock_db::text_result_t, sqlpp::result_row_t<sqlpp::field_spec_t<Test_::Id::_sqlpp_name_tag, TestId>, sqlpp::field_spec_t<Test_::Symbol::_sqlpp_name_tag, sqlpp::text>>>::result_t' requested here 166 | return {statement_handler_t{}.select(std::forward<Statement>(self), db)}; | ^ include/sqlpp23/core/query/statement_handler.h:38:47: note: in instantiation of function template specialization 'sqlpp::select_result_methods_t<sqlpp::column_t<sqlpp::table_t<Test_>, Test_::Id>, sqlpp::column_t<sqlpp::table_t<Test_>, Test_::Symbol>>::_run<const sqlpp::statement_t<sqlpp::select_t, sqlpp::select_column_list_t<std::tuple<>, std::tuple<sqlpp::column_t<sqlpp::table_t<Test_>, Test_::Id>, sqlpp::column_t<sqlpp::table_t<Test_>, Test_::Symbol>>>, sqlpp::from_t<sqlpp::table_t<Test_>>, sqlpp::no_where_t, sqlpp::no_group_by_t, sqlpp::no_having_t, sqlpp::no_order_by_t, sqlpp::no_limit_t, sqlpp::no_offset_t, sqlpp::no_union_t, sqlpp::no_for_update_t> &, sqlpp::mock_db::connection_base>' requested here 38 | return std::forward<Statement>(statement)._run(db); | ^ include/sqlpp23/mock_db/text_result.h:106:8: note: candidate function not viable: no known conversion from 'TestId' to 'bool &' for 2nd argument 106 | void read_field(size_t index, bool& value) { | ^ ~~~~~~~~~~~ include/sqlpp23/mock_db/text_result.h:111:8: note: candidate function not viable: no known conversion from 'TestId' to 'double &' for 2nd argument 111 | void read_field(size_t index, double& value) { | ^ ~~~~~~~~~~~~~ include/sqlpp23/mock_db/text_result.h:115:8: note: candidate function not viable: no known conversion from 'TestId' to 'int64_t &' (aka 'long &') for 2nd argument 115 | void read_field(size_t index, int64_t& value) { | ^ ~~~~~~~~~~~~~~ include/sqlpp23/mock_db/text_result.h:119:8: note: candidate function not viable: no known conversion from 'TestId' to 'uint64_t &' (aka 'unsigned long &') for 2nd argument 119 | void read_field(size_t index, uint64_t& value) { | ^ ~~~~~~~~~~~~~~~ include/sqlpp23/mock_db/text_result.h:123:8: note: candidate function not viable: no known conversion from 'TestId' to 'std::span<const uint8_t> &' (aka 'span<const unsigned char> &') for 2nd argument 123 | void read_field(size_t index, std::span<const uint8_t>& value) { | ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ include/sqlpp23/mock_db/text_result.h:129:8: note: candidate function not viable: no known conversion from 'TestId' to 'std::string_view &' (aka 'basic_string_view<char> &') for 2nd argument 129 | void read_field(size_t index, std::string_view& value) { | ^ ~~~~~~~~~~~~~~~~~~~~~~~ include/sqlpp23/mock_db/text_result.h:134:8: note: candidate function not viable: no known conversion from 'TestId' to 'std::chrono::sys_days &' (aka 'time_point<std::chrono::system_clock, duration<long, ratio<86400>>> &') for 2nd argument 134 | void read_field(size_t index, std::chrono::sys_days& value) { | ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ include/sqlpp23/mock_db/text_result.h:162:8: note: candidate function not viable: no known conversion from 'TestId' to '::sqlpp::chrono::sys_microseconds &' (aka 'time_point<std::chrono::system_clock, duration<long, ratio<1, 1000000>>> &') for 2nd argument 162 | void read_field(size_t index, ::sqlpp::chrono::sys_microseconds& value) { | ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ include/sqlpp23/mock_db/text_result.h:190:8: note: candidate function not viable: no known conversion from 'TestId' to '::std::chrono::microseconds &' (aka 'duration<long, ratio<1, 1000000>> &') for 2nd argument 190 | void read_field(size_t index, ::std::chrono::microseconds& value) { | ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ include/sqlpp23/mock_db/text_result.h:219:8: note: candidate template ignored: could not match 'std::optional<T>' against 'TestId' 219 | auto read_field(size_t index, std::optional<T>& value) -> void { | ^ 1 error generated.As you can see in the example, I am implementing the to_sql_string function, I expected something like a from_sql_string to do the other way around.
With sqlpp11 I had implementation of different data_types which handled exactly this. Hopefully this functionality can be implemented in sqlpp23!
Thank you for the wonderful library!
Regards, Matthijs